<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>output标签</title>
</head>
<body>
<form oninput="out.value=parseInt(num1.value)*parseInt(num2.value)">
    <input type="number" id="num1" value="50">*<input type="number" id="num2" value="60">
    =<output name="out" for="num1 num2"></output>
</form>
</body>
</html>